Two energetically disparate folding pathways of -lytic protease
share a single transition state
Alan I. Derman
& David A. Agard
The Howard Hughes Medical Institute and the Department
of Biochemistry and Biophysics, University of California, San Francisco,
513 Parnassus Avenue, Box 0448, San Francisco, California
94143-0448, USA.
The Lysobacter enzymogenes-lytic protease (LP) is
synthesized with a 166 amino acid pro region (Pro) that catalyzes the folding
of the 198 amino acid protease into its native conformation. An extraordinary
feature of this system is the very high energy barrier (G = 30 kcal
mol-1) that effectively prevents LP from folding
in the absence of Pro (t1/2 = 1800 years). A pair of mutations
has been isolated in the protease that completely suppresses the catalytic
defect incurred in Pro by truncation of its last three amino acids. These
mutations also accelerate the folding of LP in the absence of Pro by
400-fold. An energetic analysis of the two folding reactions indicates that
the mutations stabilize the transition states of both the catalyzed and uncatalyzed
folding reactions by 3 kcal mol-1. This finding points
to a single transition state for these two distinct and energetically disparate
folding pathways, and raises the possibility that all LP folding pathways
share the same transition state.
-lytic protease
share a single transition state
-lytic protease (
G = 30 kcal
mol-1) that effectively prevents 
